In January 1999 scientists were left scratching their heads by unusual solar flare bursts which appeared to be falling into the sun. These strange eruptions were unlike regular solar flares which burst outward from the sun's surface. Over two decades later a new study using 3D simulations has discovered how these mysterious solar flares work. Described as 'downward-moving dark voids' the reverse flares were caused by the inability of different densities of plasma to mix, similar to how oil and water separate after mixing. Researchers believe learning more about this kind of solar activity could help develop a means to forecast space weather.